Biodiversité et abondance du zooplancton gélatineux le long de la côte algérienne

La distribution du zooplancton gélatineux (Siphonophorae, Salpidae, Doliolidae, Appendicularia, Chaetognatha et Mollusca) a été étudiée durant les quatre saisons sur un ensemble de stations le long de la côte algérienne. Sur 56 espèces reconnues, la diversité a été plus grande au printemps et l’abondance a été plus importante au printemps et en été. La composition taxinomique a varié selon les saisons : les assemblages printaniers ont été plus diversifiés, comprenant essentiellement des espèces de Thaliacea ; les assemblages d’été ont été dominés par Doliolum nationalis et Flaccisagitta enflata ; les assemblages d’automne ont été caractérisés par les deux espèces gélatineuses les plus abondantes et les plus fréquentes (F. enflata et Oikopleura longicauda); et les assemblages d’hiver ont été caractérisés par des espèces carnivores.Gelatinous zooplankton (Siphonophorae, Salpidae, Doliolidae, Appendicularia, Chaetognatha, and Mollusca) distribution was investigated over four seasons at several stations along the Algerian coast. Of 56 species recognized, diversity was greatest during spring, and abundance greatest during spring and summer. Taxonomic composition varied among seasons: spring assemblages were most diverse, essentially comprising species of Thaliacea; summer assemblages were dominated by Doliolum nationalis and Flaccisagitta enflata; autumn assemblages were characterized by two most abundant and frequently found gelatinous species (F. enflata and Oikopleura longicauda); and winter assemblages were characterized by carnivorous species

Population structure, reproduction and exploitation of the greater forkbeard Phycis blennoides (Brünnich, 1768) from the Algerian basin★

The objective of this study was to determine the population distribution and some biological aspects for fish stock assessment of the greater forkbeard Phycis blennoides along the Algerian basin. The distribution of P. blennoides (3418 individuals) was studied using data collected between 170–779 m depth during two bottom trawl surveys developed on 2003 and 2004. Additionally, some biological parameters were obtained from 1050 individuals sampled from commercial fisheries in Algerian ports (i.e. Annaba, Azeffoun, Dellys, Cap Djinet, Zemmouri, Bouharoun, Algiers, La Madrague, Cherchell, Tenes and Mostaganem) during the period 2013–2017. P. blennoides sampled from bottom trawl surveys showed a depth related distribution with the largest individuals being found at 600–800 m depth and the smallest at shallower depths. Density and biomass varied with depth and density also with longitude, while biomass showed no pattern with longitude. Recruitment was recorded in the eastern sector of Algeria during winter, for individuals sampled by bottom trawl surveys. Young P. blennoides entered commercial fisheries in summer, with an overall sex ratio skewed towards males (1F:2.18M). The size at first maturity (L 50) was 24.30 cm and 30.39 cm for males and females, respectively. The age at 50% maturity was 2–3 years for specimens collected by a bottom trawl survey in 2003 and commercial fisheries, but 3–4 years for the bottom trawl survey in 2004

Biodiversity and abundance of gelatinous zooplankton along the Algerian coast

Gelatinous zooplankton (Siphonophorae, Salpidae, Doliolidae, Appendicularia, Chaetognatha, and Mollusca) distribution was investigated over four seasons at several stations along the Algerian coast. Of 56 species recognized, diversity was greatest during spring, and abundance greatest during spring and summer. Taxonomic composition varied among seasons : spring assemblages were most diverse, essentially comprising species of Thaliacea ; summer assemblages were dominated by Doliolum nationalis and Flaccisagitta enflata ; autumn assemblages were characterized by two most abundant and frequently found gelatinous species (F. enflata and Oikopleura longicauda) ; and winter assemblages were characterized by carnivorous species.Biodiversité et abondance du zooplancton gélatineux le long de la côte algérienne. La distribution du zooplancton gélatineux (Siphonophorae, Salpidae, Doliolidae, Appendicularia, Chaetognatha et Mollusca) a été étudiée durant les quatre saisons sur un ensemble de stations le long de la côte algérienne. Sur 56 espèces reconnues, la diversité a été plus grande au printemps et l’abondance a été plus importante au printemps et en été. La composition taxinomique a varié selon les saisons : les assemblages printaniers ont été plus diversifiés, comprenant essentiellement des espèces de Thaliacea ; les assemblages d’été ont été dominés par Doliolum nationalis et Flaccisagitta enflata ; les assemblages d’automne ont été caractérisés par les deux espèces gélatineuses les plus abondantes et les plus fréquentes (F. enflata et Oikopleura longicauda) ; et les assemblages d’hiver ont été caractérisés par des espèces carnivores.Khames Ghollame Ellah Yacine, Hafferssas Aziz. Biodiversity and abundance of gelatinous zooplankton along the Algerian coast . In: Revue d'Écologie (La Terre et La Vie), tome 73, n°3, 2018. pp. 211-226

Temporal patterns of gelatinous zooplankton distribution and environmental drivers in the south-western Mediterranean Sea

This study aims to investigate the distribution of gelatinous zooplankton in relation to environmental parameters along the coastal regions of Algeria in the south-western Mediterranean Sea. A total of 48 species were recorded from nine sampling stations located in the central (Sidi Fredj) and western (Habibas Islands) sectors of the Algerian coast. The results showed that the seasonal distribution of gelatinous species exhibits significant variations. Amongst cnidarians, P. noctiluca, M. atlantica and A. tetragona are the most abundant species. Chaetognaths are primarily represented by F. enflata and P. friderici. Tunicates display high diversity, with T. democratica, O. longicauda and D. nationalis as the most abundant species. Lastly, in molluscs, H. inflatus and L. trochiformis are the most abundant species. The nMDS and ANOSIM analysis reveal significant differences in the ecological community structures between the Habibas Islands and Sidi Fredj. Redundancy analysis results show relationships between different marine species and environmental variables, such as temperature, chlorophyll a and salinity. The studied species exhibit positive or negative correlations with these variables, suggesting an influence of these factors on their abundance and distribution. This study enhances our understanding of the factors that govern the distribution and dispersal of gelatinous zooplankton in the Mediterranean Sea and has significant implications for predicting changes in the distribution of these species under future environmental scenarios

Global extreme wave estimates and their sensitivity to the analysed data period and data sources

In the absence of wave measuring buoys operating over extended periods, wave hindcast data or satellite observations are indispensable for estimating global extreme wave heights. However, the results may depend on the analysed wind wave sources and the period's length. The sensitivity of the estimated extreme significant wave heights (SWH) to the analysed data sources and periods is investigated in this study. Global extreme wave heights are estimated using ECMWF Reanalysis v5 data (ERA5), global wave hindcast developed based on Simulating WAves Nearshore forced by the Japanese 55-year Reanalysis (SWAN-JRA55), satellite altimeter observations, and long-term wave buoy measurements. Both Annual Maximum fitting to the Generalized Extreme Value Distribution (AM-GEV) and Peaks Over Threshold fitted to the Generalized Pareto Distribution (POT-GPD) models are used. The results show that the global extreme SWH estimates considerably depend on the analysed data sources. The relative differences observed between the analysed data sources are >20% in large parts of the world. Thus, the relative differences in extreme SWH are mainly lower by increasing the analysed data periods. However, they can reach 30% and are more critical using AM-GEV. Besides, by comparing the extreme values from reanalysis and hindcast wave data to those from long-term wave measurements, underestimations of up to 2 m are observed for a return period of 100 years in the North-West Atlantic and North-East Pacific

Population structure, reproduction and exploitation of the greater forkbeard

The objective of this study was to determine the population distribution and some biological aspects for fish stock assessment of the greater forkbeard Phycis blennoides along the Algerian basin. The distribution of P. blennoides (3418 individuals) was studied using data collected between 170–779 m depth during two bottom trawl surveys developed on 2003 and 2004. Additionally, some biological parameters were obtained from 1050 individuals sampled from commercial fisheries in Algerian ports (i.e. Annaba, Azeffoun, Dellys, Cap Djinet, Zemmouri, Bouharoun, Algiers, La Madrague, Cherchell, Tenes and Mostaganem) during the period 2013–2017. P. blennoides sampled from bottom trawl surveys showed a depth related distribution with the largest individuals being found at 600–800 m depth and the smallest at shallower depths. Density and biomass varied with depth and density also with longitude, while biomass showed no pattern with longitude. Recruitment was recorded in the eastern sector of Algeria during winter, for individuals sampled by bottom trawl surveys. Young P. blennoides entered commercial fisheries in summer, with an overall sex ratio skewed towards males (1F:2.18M). The size at first maturity (L 50) was 24.30 cm and 30.39 cm for males and females, respectively. The age at 50% maturity was 2–3 years for specimens collected by a bottom trawl survey in 2003 and commercial fisheries, but 3–4 years for the bottom trawl survey in 2004